1. Field of the Invention
The present invention relates to a turntable assembly for driving the rotation of a mini disk (MD) or other information storage disk, more particularly relates to an improvement of the centering mechanism for an information storage disk on a turntable.
2. Description of the Related Art
The turntable assembly disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2000-113544 and Japanese Unexamined Patent Publication (Kokai) No. 2000-251361, as shown in FIG. 1A and FIG. 1B, has a motor 1 having a projecting motor shaft 1a and a plastic turntable 2 having a center hole 2a into which the projecting portion of the motor shaft 1a is inserted and a magnet holding groove 2c formed at the disk hole mating hub 2b around the center hole 2a. The magnet holding groove 2c holds a permanent magnet 2d for clamping the information storage disk placed on the turntable 2. The disk centering mechanism of the turntable assembly is comprised of a plurality of centering hooks K formed at equal intervals in the circumferential direction at the outer circumference of the disk hole mating hub 2b of the plastic turntable and leaf springs F for bottom support giving an elastic spring force upward to the centering hooks K at the back surface of a thin disk flange 2e. Each centering hook K is comprised of an elastic tongue K1 defined by a U-shaped slit S seen from the plan view straddling the disk hole mating hub 2b and the disk flange 2e and a hook K2 rising up at the top surface of the inside end of the elastic tongue K1. Due to the flexibility given by the plastic elasticity of the elastic tongue K1, the hook K2 can flex in the axial center direction. The reason for elastically pushing the centering hooks K upward by the leaf springs F is that a creep phenomenon where the plastic centering hooks K absorb moisture and lose elasticity is liable to occur under a high humidity environment, so this enables the plastic elasticity of the elastic tongues K1 to be reduced.
Summarizing the problems to be solved by the invention, there have been the following problems in a disk centering mechanism using the above plastic centering hooks K and leaf springs F:
First, since the centering hooks K are in the final analysis supported at the bottom by the elastic spring force of the leaf springs F, they are only significant as pushing members for elastically contacting the inner circumference of the disk hole and pushing on it outward in the radial direction joined with the turntable 2, but formation of the centering hooks K on the turntable 2 complicates the mold structure and invites a rise in the mold cost.
Second, the leaf springs F for supplementary elastic spring force have to be bonded or welded to the back surface side of the center hole 2a of the turntable 2 before fitting the center hole 2a of the turntable 2 over the motor shaft 1a. Not only is this complicated, but also variation in the mounting accuracy or press fit strain arising when fitting the center hole 2a of the turntable 2 over the motor shaft 2 etc. cause variation in the supplementary elastic spring force, so strictness is required in the work of attaching the leaf springs. This invites a drop in the work efficiency.
A first object of the present invention is to provide a turntable assembly having a disk centering mechanism not requiring use of plastic centering hooks and able to simplify the mold structure.
A second object of the present invention is to provide a turntable assembly enabling the leaf springs for giving elastic spring force in the disk centering mechanism to be attached even after fitting the center hole of the turntable over the motor shaft.
In the present invention, the inventors came up with the idea of providing the leaf springs for imparting elastic spring force in the disk centering mechanism on the upper side of the turntable. That is, the turntable assembly according to the present invention has a motor having a projecting motor shaft and a turntable having a center hole into which the projecting portion of the motor shaft is inserted and a magnet holding groove formed at a disk hole mating hub around the center hole and has a permanent magnet for clamping an information storage disk placed on the turntable in the magnet holding groove. In the present invention, the disk hole mating hub has a plurality of spring seats at spring flexing spaces formed at intervals in the circumferential direction, each of the spring seats is provided with a centering leaf spring having a front end protruding slightly outward in the radial direction from the circumference of the disk hole mating hub, and a front end of each centering leaf spring elastically contacts an inner circumference of the disk hole and pushes on it outward in the radial direction when the disk hole of the information storage disk is mated with the disk hole mating hub.
Due to this configuration, since no plastic centering hooks are used, not only is there no problem in creep phenomenon etc., but also it is possible to simplify the mold structure and possible to realize a reduction in mold cost. Further, since the centering leaf springs are provided at the spring seats at the spring flexing spaces, it is possible to attach the centering leaf springs even after fitting the center hole of the turntable over the motor shaft, so the efficiency of the assembly work can be improved.
Here, to further improve the efficiency of the work of attaching the centering leaf springs, it is preferable that the base ends of the centering leaf springs be fixed by an insert type spring holder from above. It is possible to attach the centering leaf springs by just inserting the insert type spring holder.
As an insert type spring holder, it is possible to use the clamping use permanent magnet holding the base ends of the centering leaf springs with the outer inner circumference of the magnet holding groove. It is possible to keep from adding a special part as the insert type spring holder and therefore to reduce the costs. Since it is possible to use the attachment operation of the permanent magnet, the attachment work can be streamlined. Further, since the centering leaf springs can be made of phosphor bronze, stainless steel, or another magnetic material, it is possible to use the attraction force of the clamping use permanent magnet for attaching the centering leaf springs in addition to insertion.
The assembly can have a back yoke below the permanent magnet in the magnet holding groove, and the insert type spring holder can be made the back yoke holding the base ends of the centering leaf springs with the outer inner circumference of the magnet holding groove.
If the plurality of centering leaf springs are separate parts, the positioning etc. become complicated, so the plurality of centering leaf springs preferably are integrally connected to a flat ring. The support ring is preferably fit over the motor shaft laid over a bottom surface of the permanent magnet in the magnet holding groove. Since the centering leaf springs are fixed not only at their base ends, but also at the support ring, the mounting accuracy of the centering leaf springs can be standardized. Further, it is possible to make joint use of this as a back yoke. The support ring may also be held between the top surface of a back yoke held in the magnet holding groove and a bottom surface of the permanent magnet.
The front end of each centering leaf spring may be made a vertically descending piece in facial contact with the inner circumference of the disk hole. Further, a flex point of the centering leaf spring is preferably between an outside angular part of the spring seat and an upward taper of an outer circumference of the disk hole mating hub. Since the flex point of the centering leaf spring can be positioned relatively far from the front end contacting the inner circumference of the disk hole, the arc of the front end accompanying flexing of the centering leaf spring can be made larger and the inner circumference of the disk hole can be pushed on outward in the radial direction.